Modifying the w3nqn cw pasive audio filter to interface with your computer sound card so that you can use your cw keyer's sidetone audio to send high quality morse code audio tones to the LINE IN or MIC IN input of your sound card

Modifying the w3nqn cw pasive audio filter to

interface with your computer sound card so

that you can use your cw keyer's

sidetone audio to send high quality morse

code audio tones to the LINE IN or MIC IN

input of your sound card and send morse

code over the internet on iCW

using your paddles, bug or key

THIS TYPICAL KEYER

PLUS THIS MODIFIED W3NQN FILTER

NOTE: get the w3nqn parts for this modified filter for $23 from Ed's(w3nqn) special offer HERE

GOES FROM

THIS RASPY AUDIO

TO THIS SMOOTH AUDIO !

Listen to the difference between these two [ using LINE IN jack of sound card ]

NOTE: all audio files in this article were recorded after being sent out to the internet and received back into the MUMBLE client

Here is the unfiltered audio from the LOGIKEY K-1 cw keyer

UNFILTERED AUDIO

Here is the filtered audio of the LOGIKEY K-1 cw keyer

after using the w3nqn cw audio filter (INPUT = LINE IN JACK )

FILTERED AUDIO

- THE LINE IN JACK WORKS BEST -

HOWEVER, IF ALL YOU HAVE IS A MIC IN JACK

there are special instructions below

Listen to these keyers (with internal speakers)

using the MIC IN jack of a laptop

Here is the filtered audio from the

LOGIKEY K-1

and the w3nqn cw audio filter

using paddles (input = MIC IN JACK )

Here is the filtered audio from the

MFJ 451

and the w3nqn cw audio filter

using paddles (input = MIC IN JACK )

Here is the filtered audio from the

Heathkit Code Oscillator HD-1416

and the w3nqn cw audio filter

using a straight key (input = MIC IN JACK )

Here is the filtered audio from the

K1EL K-40

and the w3nqn cw audio filter

using paddles (input = MIC IN JACK )

NOTE: The K1EL K-40 has an additional speaker jack available - "AF" in the diagram below - you don't have to unsolder its speaker wires,

but during construction of the k-40 kit, you will have to attach wires from the circuit board at "AF" to one of the RCA jacks on the back

LOOK AT THE BEFORE AND AFTER PICTURES OF THE CW AUDIO WAVEFORM ON THE K1EL K-40

BEFORE FILTERING

AFTER FILTERING

HERE IS HOW [LINE IN JACK]

(this should work on any cw keyer that has a speaker or speaker jack )

1. unsolder the wires to the speaker inside your cw keyer

2. connect a cable from those "unsoldered speaker wires" to the input of the w3nqn cw audio filter input transformer (for ground loop isolation, do not connect the grounds of the primary and secondary windings of this transformer)

3. do not connect the output audio transformer that comes with the w3nqn cw audio filter kit...(or remove it if attached)

4. instead connect a 200 ohm resistor to the output of the w3nqn cw audio filter to ground. (You can also use the modified circuit below described for the MIC IN method)

5. then connect a cable from the w3nqn output terminals to the sound card's LINE IN jack. (A mono to stereo audio adapter will allow you to hear your side tone in both LEFT and RIGHT speakers/headphones - (since all LINE IN Jacks are stereo input) Here are a couple of RADIO SHACK parts as an example 1 2 ) Hook up your paddles, its testing time.

6. to hear your sidetone, "unmute" your playback volume mixer on the LINE IN column and adjust the slider until you have enough volume - to your preference - you will now hear your sidetone from your computer speakers or headphones instead of the speaker in your keyer

7. Load MUMBLE:

you are now ready to send cw over iCW

bring up your sound card recording volume mixer and put a checkmark in the LINE IN column. On the mumble CONFIGURE/SETTINGS/AUDIO-input - select the sound card where your LINE IN jack will be used...

8. ACTIVATE the MUMBLE LOOPBACK TEST

*Listen to how you sound over mumble through the iCW server*

- adjust your LINE IN recording volume mixer slider until you have just enough volume to reach full volume in mumble

(my setting was 80 % to reach full volume over mumble)

- once you have established the correct threshold setting for full volume over mumble, get out of the LOOPBACK TEST

9 you are now ready to send cw over iCW using your paddles, key or bug and your keyer

10 Enjoy your morse code on iCW !

HERE IS HOW [ MIC IN JACK ]

(this should work on any cw keyer that has a speaker or speaker jack)

FOR MIC IN use this :

[MONO MIC INPUT ONLY]

[most computer mics are MONO]

NOTE:

- The MIC IN is much more sensitive and needs a lot less input voltage.

- The ground of the primary input transformer is isolated from the

ground of the secondary windings of the input transformer and the rest

of the circuit

- *If you do have a stereo microphone input on your computer sound card,

you can use a mono to stereo audio adapter so you can hear your sidetone

in both the left and right speaker*

- the variable 300 ohm resistor followed by the series 1k resistor and the .22 uf cap,

will help reduce the noise and allow you to adjust the volume low enough to get best results.

(this circuit modification after testing, also seems to work well with the LINE IN jack too)

On your RECORDING VOLUME MIXER for your sound card , keep the slider that controls the input volume as LOW as possible; so that it will minimize as much as possible, how much background hiss, hum, and other noises that the sound card broadcasts - even with no signal

Most sound cards will have a certain amount of background "noise" that is present, even with no signal input. The lower you can adjust your RECORDING VOLUME MIXER for the MIC or LINE input, the lesser the "noise" that will leak through and get transmitted along with your CW audio tones. The correct amount of "volume" for the input to mumble, is that which is just below the volume that "kick starts" the mumble AGC software circuit. Your volume will be at near maximum at this point with the advantage that you will not get a pop or click from every first cw note due to your volume being too loud and causing the mumble AGC to activate.

VERY IMPORTANT !

all volumes must be adjusted properly or distortion will result ...

On my working setup:

- I set the windows RECORDING VOLUME MIXER MICROPHONE SLIDER all the way down...

- I set the 300 ohm pot to where it was just under the amount of volume that would activate the MUMBLE AGC circuit ( you have to use the MUMBLE LOOPBACK selection and listen to your cw while sending and adjusting the 300 ohm potentiometer as you send....when you notice that by lowering your volume, the MUMBLE AGC no longer can bring your volume back up again, that is the point just under the AGC ACTIVATION POINT. Try to get close to this point.

- instead of listening to your keyer / paddle sidetone on your keyer speaker ...you have to listen to your keyer sidetone using your computer speakers now...

all you have to do is UN-MUTE the MICROPHONE column on your windows PLAYBACK volume mixer and adjust the loudness of that slider to your preference

We are only going to use the TIP and the SHIELD for connection to the output terminals of the w3nqn filter (for the MONO MIC input )

The middle section of the stereo MIC plug we don't use, ( it is normally used for remote voltage to a condensor mic)

[ the typical maximum voltage for MIC IN is @ 50 milli volts ]

- cw audio output from the cw keyer to the input of the w3nqn filter

- cw audio output from the w3nqn filter to the input of the sound card

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